genirq: Implement irq_percpu_is_enabled()

Certain interrupt controller drivers have a register set that does not
make it easy to save/restore the mask of enabled/disabled interrupts
at suspend/resume time. At resume time, such drivers rely on the core
kernel irq subsystem to tell whether such or such interrupt is enabled
or not, in order to restore the proper state in the interrupt
controller register.

While the irqd_irq_disabled() provides the relevant information for
global interrupts, there is no similar function to query the
enabled/disabled state of a per-CPU interrupt.

Therefore, this commit complements the percpu_irq API with an
irq_percpu_is_enabled() function.

[ tglx: Simplified the implementation and added kerneldoc ]

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Tawfik Bayouk <tawfik@marvell.com>
Cc: Nadav Haklai <nadavh@marvell.com>
Cc: Lior Amsalem <alior@marvell.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: Gregory Clement <gregory.clement@free-electrons.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: http://lkml.kernel.org/r/1445347435-2333-2-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 25 insertions, 0 deletions

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 0eebaeef317b..c84670c373f9 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1743,6 +1743,31 @@ out:
 }
 EXPORT_SYMBOL_GPL(enable_percpu_irq);
 
+/**
+ * irq_percpu_is_enabled - Check whether the per cpu irq is enabled
+ * @irq:	Linux irq number to check for
+ *
+ * Must be called from a non migratable context. Returns the enable
+ * state of a per cpu interrupt on the current cpu.
+ */
+bool irq_percpu_is_enabled(unsigned int irq)
+{
+	unsigned int cpu = smp_processor_id();
+	struct irq_desc *desc;
+	unsigned long flags;
+	bool is_enabled;
+
+	desc = irq_get_desc_lock(irq, &flags, IRQ_GET_DESC_CHECK_PERCPU);
+	if (!desc)
+		return false;
+
+	is_enabled = cpumask_test_cpu(cpu, desc->percpu_enabled);
+	irq_put_desc_unlock(desc, flags);
+
+	return is_enabled;
+}
+EXPORT_SYMBOL_GPL(irq_percpu_is_enabled);
+
 void disable_percpu_irq(unsigned int irq)
 {
 	unsigned int cpu = smp_processor_id();